Studies on the evolution of the bacterial genome are continuing. For the coming year we plan to (1) investigate the presence of intragenomic homologies that may reflect gene or genome duplications in the evolutionary past, (2) investigate the effect of gene location on gene function by engineering directed transpositions with the E. coli genome, (3) study species divergence of two enteric bacteria by a comparative analysis of a selected region of the two genomes, (4) study the evolutionary relationships between the genomes of representative members of the Enterobacteriaceae, using techniques of DNA-DNA hybridization. Genetic mapping of Serratia marcescens will also continue. Through these various experimental approaches, we hope to find out more about the various mechanisms that have operated during the evolution of the bacterial genome.